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Sex Ratio, Fecundity and Gonado Somatic Index of Spotted Snakehead, Channa Punctatus (channidae) from a Lentic Ecosystem

Sohel Mian
Department of Fish Biology and Genetics, Sylhet Agricultural University, Sylhet, Bangladesh

Mohammad Amzad Hossain
Department of Fish Biology and Genetics, Sylhet Agricultural University, Sylhet, Bangladesh

Abdul Wahab Shah
Department of Fish Biology and Genetics, Sylhet Agricultural University, Sylhet, Bangladesh

Abstract/ Executive Summary:

Sex ratio, fecundity and gonado somatic indices give important clue about any fish’s reproductive biology. The study was conducted to know the sex ratio, fecundity and gonado somatic index of spotted snakehead, Channa punctatus from a closed water body. Data on male-female ratio, fecundity and gonado somatic indices were calculated round the year. Fish samples were caught using the traditional cast nets from the earthen ponds. The female to male sex ratio for spotted snakehead in closed ecosystem found to be 1.16:1. Fecundity ranged from 2538±51 to 32987±111.52 and peak value was recorded in July. The highest mean gonado somatic index was 5.34±0.07 for female and 0.49±0.04 for male in July, showing that the gonadal development reached its peak during this month. Monthly pooled values of GSI indicated that the peak breeding season of C. punctatus occurred in the month of July in closed waterbody like earthen pond. The results of the present study revealed that C. punctatus breeding season starts from April and ends in September i.e., the rainy season in Bangladesh. The observation of the present study will be helpful for selective breeding programme, conservation and sustainable fishery management of C. punctatus in its natural waterbodies.

Keywords: Sex ratio, Gonado somatic index, Spotted snakehead, Channa punctatus, Lentic ecosystem

Location: Sylhet Agricultural University, Sylhet, Bangladesh

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Snake head

Objectives:

Information on reproductive characteristics will be helpful to conserve this fish in the wild condition. It is easy to ascertain the spawning season of a fish by studying the seasonal changes of the fecundity and gonado somatic indices. The current initiative was undertaken to determine the gonad maturity and spawning period influenced by different seasons in C. punctatus.

Methodology:

2.1 Study area: The study area was Sylhet Agricultural University, Sylhet, Bangladesh and is located between 24°54' North latitude and 91°54' East longitude.

2.2 Collection of specimens and sampling Samples of C. punctatus were collected fortnightly from small ditches of Sylhet Agricultural University campus. The specimens were collected for one year. The simple random sampling technique was used. A total of 312 samples were collected during the study period. The samples were transported to the laboratory and preserved in a deep freezer at -20°C until examination and analysis.

2.3 Body measurements The specimens were taken out of the deep freezer and allowed to thaw and the body length and weight were measured. Total and standard lengths were measured using a one-meter measuring board graduated in cm. The fish was wiped with a dry napkin before weighing and body weight and ovary weight were measured using a weighing balance (model: GemPro 250 digital gems scale).

2.4 Sex ratio Each specimen was dissected and the gonads were removed. The sex of each specimen was identified by examination of the gonads. The proportion of the two sexes relative to one another was used to calculate the sex ratio.

2.5 Gonadosomatic index A total of 312 (Female 165; Male 147) C. punctatus from lentic ecosystem were collected and maintained in accordance with the guidelines of the Sylhet Agricultural University. The gonads were removed by abdominal dissection and weighed to the nearest gram. The gonado somatic index (GSI) was obtained according to the following equation: GSI =GW/ (TW-GW) x 100 Where, GW= gonad weight, and TW= total body weight. Then the gonad samples were preserved in 10 % buffered formalin and kept at room temperature for further use.

2.6 Fecundity To estimate the fecundity, three sub-samples of ovaries weighing 0.1 g to 0.2 g were obtained from the anterior, posterior and the middle of gonad. The eggs were placed into a dish and counted under stereo light microscope (Nikon, YS100). The mean from the three sub-samples were used to calculate absolute and relative fecundity using gravimetric method. Fecundity was calculated by the following formula: F = n × G/ g Where “F” is fecundity, “n” is the average number of eggs in sub-sample, “G” is weight of the gonads and “g” is the weight of the sub-sample.

Source of Information: International Journal of Fisheries and Aquatic Studies 2017; 5(1): 360-363

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Overall, the fecundity and gonado somatic index of C. punctatus in the different seasons in a lentic ecosystem found to be different. The high values of GSI appeared from March to July for both male and female with the peak in July, indicating the onset of the reproductive season. It is expected that the information generated in the current study will contribute better understanding of gonad developmental cycle of C. punctatus towards conservation action plans and rearing in captivity.

Knowledge Management: Journal